Yup, ditto what others have said here. This has been a problem ever since eBay Labels became a thing in Canada. eBay allows customers to check out using an address written in non-Latin characters, but Canada Post's software isn't set up to handle non-Latin characters. Canada Post's addressing guidelines also specify an English translation of the address should be on the package.
Just ask the buyer for an English translation of their address and they should be able to provide one. Worst case scenario - if the buyer isn't responding to you and you don't want to cancel the sale - use a translation site or AI of your choice to translate the address into English characters. And it's a good idea to print out and tape an image of their Japanese character address next to the English address as well.
I just had the exact same problem as you last month. In my case, the buyer was not responding to my messages requesting an English translation of the address, so I cancelled the order with reason "problem with buyer's address". The buyer ended up reaching out about a week after I cancelled it to try and rectify the situation, but it was several days of back-and-forth trying to explain that he had been refunded for the order and needed to repurchase it if he still wanted it. Ultimately I think the issue was eBay's built-in chat translation being terrible. As soon as I started translating my messages into Japanese myself using ChatGPT and copying and pasting the Japanese language messages into the chat, he fully understood what I was trying to say and repurchased the item. Got to him in Japan in like a week, too! In hindsight I should have just translated the address myself and not bothered the customer in the first place. It was a $12 DVD it wasn't worth all the effort lol (and the translated English address he eventually provided was basically the same as the one ChatGPT gave me when I told it to translate his Japanese address).
